Metal working process



United States Patent 3,250,103 METAL WORKING PROCESS Stewart James Beanbien, Oakland, Calif., and Neville Harold George Daniels, Petone, Wellington, New Zealand, assignors to Shell Oil Company, New York, N.Y., a corporation of Delaware No Drawing. Filed Jan. 30, 1964, Ser. No. 341,405 15 Claims. (Cl. 72-42) This invention relates to a process for forming metal and in particular to metal drawing.

In a process for drawing metals, a lubricant is generally employed to lubricate dies and work piece. The action of a drawing lubricant has .a practical value. With the application of a proper drawing lubricant between work metal and dies, friction and surface damage to both die and work piece are materially reduced. If not controlled, high friction could result in oifsize and damaged work pieces and shorter service life of the die setup.

Many lubricants have been proposed for drawing metals. In general the various types of lubricants which have been proposed include soft metals, principally lead; solid non-metallic lubricants such as waxes, hard soap, solid greases and the like; and liquid lubricants such as mineral oils compounded with fatty materials and soaps.

, Precoating the metal with materials such as lime or phosphate is also known.

In a widely applied process for drawing metals, the metal to be worked is first coated with phosphate by dipping the metal into a warm phosphate solution and then rinsed. A soap lubricant such as sodium oleate or calcium stearateor the like is then applied to the phosphate coated metal and allowed to dry. The metal is then drawn through appropriate dies. Although the phosphate-soap method permits multiple reductions to a large ultimate reductionin size without intermediate relubrication, the method is objectionable in that excessive handling is required, the operation is messy and liquid and fumes from the phosphate solution are rather corrosive to the physical plant. Moreover, the reduced 'metal has a rather grey color and sometimes a quite dark color which is objectionable to those customers who desire a bright finish.

It has now been discovered that metal can be drawn to a large total reduction in size (e.g., to about 70 to 85%) and a bright finish when the Work metal is lubricated with a lubricant comprising a solid high molecular weight polymer characterized by a long carbon chain back bone and having an average molecular weight (by light scattering technique) of about 10,000 to about 1,000,000. Such polymers are prepared from oneormore monomers having from about 2-10 carbon atoms per molecule and a carbon to carbon double bond. Thepolymer can be a homopolymer or a copolymer. Highly suitable polymers are copolymers of ethylene with another monomer, e.g., propylene. such a copolymer mixed with Wax.

in the literature, such as An Introduction to the Organic Chemistry of High Polymers by Carl S.- Marvel, published by John Wiley and Sons, Inc., New York (1959). In general, the preparation of polymers is conducted at temperatures ranging from about room temperature to about 150 C. and pressures below about 500 pounds per square inch to about atmospheric pressure. Suitable catalysts are formed from a transition metal compound and metal-organic compound capable of acting as a reducing' agent.

Monomers for the production of high molecular weight I long linear carbon chain back-bone polymers are compounds having the formula RCH=CH wherein R is a hydrogen, a halogen or an organic group such as an aliphatic, cycloaliphatic, aromatic, or carboxyl group containing from 1-8 carbon atoms. Such monomers include, for example, hydrocarbons such as ethylene, propylene, and styrene; vinyl compounds such as vinyl chloride, and vinyl acetate; and the like.

Homopolymers are amorphous or highly crystalline depending upon the particular monomer used, the particular catalyst and the particular polymerization conditions. In general, monomers in which R is an unbranched C or higher alkyl group generally result in polymers which are not crystalline. Monomers known to produce stereoregular crystalline polymers are propylene, 3-methyl-lbutene, 4-methyl-1-pentane, 4-methyl-l-hexane and the like. Polymers, for example, polypropylene, having a high degree of crystallinity as measured by X-ray analysis usually contain only a very small proportion of material which is extractable in boiling hydrocarbons, such as gasoline boiling range hydrocarbons. Typically, the proportion of highly crystalline polypropylene which is extractable in boiling heptane or iso-octane is less than 10% and usually less than 5%.

Copolymers are prepared by polymerizing two or more monomers. In general, copolymers are less crystalline than the homopolymers because of greater irregularity in structure. Highly suitable copolymers are the copolymers of ethylene with other monomers having from 2-10 carbon atoms and a carbon to carbon double bond, preferably monomers such as C C alpha-olefins, vinyl compounds such as vinyl acetate, and the like. Copolymers of ethylene and propylene are preferred. Average molecular weight of the copolymers is generally from about 20,000 to 800,000 and preferably about 200,000 to 400,000.

Polymers having a long carbon chain back-bone may be prepared, for example, by the copolymerization of unsubstituted diolefins, such as butadiene, or alkyl substituted diolefins, such as isoprene, and hydrogenation of the copolymer to eliminate any remaining unsaturated An especially suitable lubricant comprises In the process of the invention, the metal to be worked is coated with a dry film of the lubricant. and is then drawn through a suitable die. The lubricant can be'applied by dipping the work piece into molten lubricant;

however, this is frequently objectionable since high temv linkages.

' In addition to being soluble in hydrocarbon solvents, the amorphous or relatively non-crystalline polymers can usually be extended with other materials such as wax to reduce the overall cost of the lubricant. To be extended with wax, polymer must be at least partially soluble in the wax. Thus, in general, linear polymers having a long carbon chain back-bone which is relatively free of hydrophilic functional groups attached thereto, such as hydroxyl andaryl groups, are suitable. Such polymers are typified by polymers of alpha-olefins, such as polyethylene and polypropylene, and the copolymers of ethylene with other monomers such as alpha-olefins, vinyl ace- I tate, and the like.

It should be noted, however, that molecular weight of a given polymer determines in large part its solubility in wax. Thus, for example, it is the relatively low molecular weight polyethylene or polypropylene which is of such low crystallinity as to be readily soluble in wax, whereas the high molecular weight polymers of polyethylene or polypropylene have a high degree of crystallinity and are much less soluble in wax. In general, the molecular Weight of the polymers which are to be extended with wax for use as a lubricant in the present process will be no greater than about 500,000 and generally much less. In any event, the Wax solubility of the given polymer is readily determined simply by heating and mixing the polymer in question with an appropriate amount of wax. In general, copolymers of ethylene are preferred and are comprised of from about 60% to 99% ethylene, usually from about 7595% ethylene.

Any suitable wax can be used to modify the polymers but in general petroleum waxes are readily available and relatively inexpensive and are preferred. The petroleum waxes are referred to in the art as paraflin wax or microcrystalline wax. Micro-crystalline .wax is also known as amorphous wax and is obtained by the dewaxing of residual lubricating oils. The paraffin waxes, are usually obtained by the dewaxing of distillate lubricating oil fractions. Distillate paraffin waxes usually have melting points between about 120 F. and 145 F., preferably between about 125-140 F. Micro-crystalline waxes which contain only minor amounts of normal paraflins and are largely highly branched and naphthenic waxes have melting points on the order of 130-160 F., usually between about 140150 F.

The higher melting point waxes 'are especially useful for blending with the lubricant used in the present invention. These include heavy distillate waxes obtained from high boiling distillate lubricating oil fractions which have melting points on the order of 145185 F., as well as the high melting point paraflin wax split from microcryst-alline wax by fractional crystallization.

It is normal practice when utilizing wax to combine several waxes together in a single composition. The purpose of this, of course, is to obtain the beneficial property inherit in each particular type of wax or to minimize adverse properties of a wax included for its other propertles.

Depending upon the nature of the particular polymer and the exact type of wax used, wax can be blended with a polymer over a wide range of concentrations. For example, it appears to be necessary or at least highly desirable to co-ordinate the unbranched chain link of the individual wax molecules with the unbranched chain link of the polymer employed. The degree of branching in a coplymer of ethylene with a higher alpha-olefin is established by the mole ratio of ethylene to the higher alphaolefin. It is desirable to have a limited spectrum of unbranched chain units in a copolymer to coordinate with the several wax species present in a normal petroleum wax.

Petroleum waxes contain a spectrum of wax species and an example of such a wax spectrum is to be found in the figires of Arabian, US Patent 2,915,447 and particularly in Table II of said patent. Thus, it can be seen that a parafiin wax having an average melting point of 123 F. contains about 86 mole percent of normal parafiins having from 22 to 27 carbon atoms per molecule. On the other hand, a paraffin wax having an average melting petroleum solvents, as a vehicle for the polymer or wax polymer blend used as a lubricant in the present process is generally objectionable from the standpoint of cost and or wax polymer blend. Suitable emulsions contain from about 1 to 15% and preferably from about 5 to 10% by weight of the lubricant in water.

Highly suitable aqueous emulsions are prepared from a blend of petroleum wax and ethylene alpha-olefin copolymer. The copolymer contains on the order of to moles of ethylene per mole of a C alpha-olefin and has an intrinsic viscosity of between about 2-5. Preferably, the copolymers are those formed from about 85- 93% of ethylene and 15-70% of a C alpha-olefin. Composition of the wax copolymer blend is from about 40-95% 'by weight of petroleum wax and from about 5-60% by weight of the copolymer. Compositions containing from about 6777% wax and 33-23% copolymer have been found to have especially good properties and are therefore preferred. The preparation of emulsions of a blend of wax and ethylene alpha-olefin copolymer is described in co-pending application by Sawyer et 211., Serial No. 277,702, filed May 3, 1963. Of course, emulsions of polymers alone without the wax can be made such as, for example, polyisoprene, polybutad-iene, ethylene and propylene copolymer, polyethylene and the like. Some are available commercially.

The invention will be understood more fully from the following tests. Unless noted otherwise, test rods used are 0.250 inch diameter AISI C1018 mild carbon steel rods, annealed in a protective atmosphere for one hour at 1650 F. The rods were drawn through a series of dies in successive draws without relubrication between draws until lubricant failure occurred as judged by the presence of surface damage on the rods. The sequence of dies (R-5 Carboloy dies, 8 angle) and reduction involved are as follows:

In the drawing tests, a thin film of lubricant was applied to the test rod by dipping the rod into a cyclohexane solution of the lubricant or an aqueous emulsion of the lubricant followed by air drying.

In test A, an ethylene-propylene copolymer (EPC) having an intrinsic viscosity of 3.1 deciliters/ g. in decalin at 150 C. and an average molecular weight of 4x10 was used as the lubricant. The ethylene-propylene mole ratio in this copolymer was 9:1. In tests B and C, this copolymer extended with Wax was used. The wax polymer mixture contained 30% wt. copolymer and 70% wt. residual paraffin wax (melting point about 183 F. and sold commercially by Shell Oil Company under the name Shellwax 700).

In test D a coplymer of ethylene and vinyl acetate sold by E. I. du Pont de Nemoursunder the name Elvax 250 was used. This copolymer was extended with petroleum wax to provide a mixture containing 30% wt. Elvax 250, 35% wt. Shellwax 700 and 35% wt. Shellwax (a paraffin wax sold by Shell Oil Company). This mixture Was applied from a hot (60 C.) cyclohexane solution since Elvax precipitates from solution if the solution is allowed to cool.

For comparison, tests were made with conventional lubricants, namely in test E, sodium oleate soap and in test F, a phosphate pretreated rod lubricated with Granolube No. 10 (a commercial product of Amchem Products, Inc.). A film of sodium oleate was deposited on the test rods by dipping the rods for five minutes in a hot (60 C.) 10% aqueous solution of the sodium oleate (99.5% purity) followed by draining and drying in air for 24 hours. In the other test, test rods were treated with zinc phosphate solution (Granodraw, a product of Amchem Products Incorporated). The phosphate treated rods, which were grey and etched to a matte finish, were lubricated With ranolube No. 10.

For comparison, drawing tests were made with another polymer. In test G, rods were dipped in a aqueous solution of a polyethylene glycol polymer sold by Carbide and Carbon Chemical Company under the name Carbowax 6. A process for drawing metal which comprises coating the metal with a lubricant consisting essentially of a polymer characterized by a long carbon chain back-bone and having an average molecular weight in the range from 6000 and allowed to dry. Carbowax 6000 is a solid poly- 5 about 20,000 to about 800,000, said polymer being a comer reported to have an average molecular weight in the polymer of ethylene with a monomer having from 2-10 range 6000-7500. carbon atoms and a carbon to carbon double bond, and

Results of the tests are given below in Table I. drawing the coated metal through a die.

T able I Drawing Drawing Speed, Force (lbs. Test No. Lubricant feet for 36%) 0.190 0.150 0.120 0.100 0.080

per Reduction minute in Area EPC ex. 2%% wt. soln in cyclohexane 1% 1, 424 Pass Pass Pass 300 1, 432 Pass Pass Pass EPC/wax ex. 4% wt. soln in cyclohexane 1% 1, 370 Pass Pass Fail 300 1,415 Pass Pass Pass EPC/wax ex. 10% wt. solids aqueous latex 1% 1, 351 Pass Pass Pass 300 1,473 Pass Pass Pass Elvax/wax ex. 4% wt. soln in eyclohexane 1% 1, 370 Pass Pass Fail 300 1,460 Pass Pass Pass Sodium oleate ex. 10% wt. aqueous soln 1% 1, 415 Pass Fail 300 1, s17 Pass Fail Phosphate pretreated, Granolube N0. 10 1% 1, 563' Pass Pass Pass 300 1,641 Pass Pass Pass Polyethylene glycol ex 10% wt. aqueous so1'n. 1% 1,403 Pass Pass Fail 300 1,420 Pass Pass Fail Wax 10% dispersion 1% 1, 347 Pass Pass Fail 300 1,454 Pass Pass Fail Total Reduction in Area 64 77 1 Commercial product of Arnchem Products, Inc.

From the' above data, it can be seen that the solid high 7. A process according to claim 6 wherein the lubrimolecular weight polymer, alone or extended with wax, cant contains from about 5% to 95% by weight wax. is much superior to soap as a drawing lubricant and is 8. Aprocess according to clairn6wherein the monomer about equal to the conventional phosphate pretreat 1s propylene. method in reduction obtained. The low molecular weight 9 A process according to claim 6 wherein the monomer polymers such as the solid polyethylene glycol are un- Vinyl acetatesuitable. In addition, the rods drawn according to the A M06655 flccordlng to 01mm t e oprocess of the invention had a bright finish, which con- 15 propylenetrasts with the grey and sometimes quite dark finish ob- 3 A Process g l to clalm 1 Whereln the tained with the phosphate pretreated rods. mg i effected. by dlPpmg the meta! Into an .aqueous We claim as our invention: 40 persion of said lubricant, and drying the dipped metal. 1. A process for drawing metal which comprises coat- A process drawmg metal i h compns.es coat the metal with a lubricant consistin essentiau of a mg the metal with a lubricant consisting essentially of 1 d 1 h d b 1 h a copolymer of ethylene and propylene containing from so 1 p0 ymer. c enze y (mg ac about 75 to 95% by weight ethylene and having an averbone and having an average molecular weight mt erange age molecular Weight of from about 20,000 to 800,000 of about 10,000 to about 1,000,000, and drawing the and drawing the coated metalthrough a Coated metal through? 13. The process according to claim 12 wherein said A P f drawlfllg metal f f comprfses Coat lubricant contains from about to 90% by weight wax. mg the metal with a lubricant consisting essentially of a 14. The process according to claim 12 wherein the coatsolid polymer characterized by a long carbon chain backing is eifected by dipping the metal into an aqueous disbone and having an average molecular weight in the range persion of said lubricant, and drying the dipped metal. from about 10,000 to about 1,000,000 and about 5% to 15 The process according to claim 13 wherein the coat- 95 by weight wax, and drawing the coated metal through mg efiectefl by lp the metal into 811 aqueous a persion of said lubricant, and drying the dipped metal.

3. The process according to claim 1 wherein the coating is efiected by dipping the metal into a liquid medium References Cited by the Exammer having said lubricant dispersed therein, and drying the UNITED STATES TS dipped metal. 2,256,603 9/ 1941 Wright 72-42 4. The process according to claim 3 wherein the liquid 2,530,838 11/1950 Orozco et a1 20519 medium is a petroleum solvent.

5. The process according to claim 3 wherein the liquid medium is water.

CHARLES W. LANHAM, Primary Examiner.

H. D. HOINKES, Examiner. 

1. A PROCESS FOR DRAWING METAL WHICH COMPRISES COATING THE METAL WITH A LUBRICANT CONSISTING ESSENTIALLY OF A SOLID POLYMER CHARACTERIZED BY A LONG CARBON CHAIN BACKBONE AND HAVING AN AVERAGE MOLECULAR WEIGHT IN THE RANGE OF ABOUT 10,000 TO ABOUT 1,000,000, AND DRAWING THE COATED METAL THROUGH A DIE. 